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Attenuation spectra of Fiber III before and after irradiation at 3 MGy. Vertical lines mark the wavelength position of Raman intensity anti-Stokes, IAS, and Stokes, IS (at 1014 nm and 1114 nm, respectively). Fig. 3. Attenuation spectra of Fiber IV (a), Fiber VI (b) and Fiber V (c) for pristine and -irradiated samples. Vertical lines mark the wavelength position of Raman intensity anti-Stokes, IAS, and Stokes, IS (at 1014nm and 1114nm, respectively).
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The integration of a Raman distributed temperature fiber-based sensors (RDTS) into the envisioned French deep geological repository for nuclear wastes, called Cigéo requires evaluating how the performances of RDTS evolve in harsh environments, more precisely in presence of H2 or γ-rays. Both H2 and radiations are shown to affect the temperature mea...
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We report on the use of second-order Raman amplification to assist a phase-sensitive optical time domain reflectometer (ΦOTDR) used for vibration measurements over very long distances. The sensor was able to measure vibrations of up to 380 Hz (limit set by the time of flight of light pulses) in a distance of 125 km with a resolution of 10 m and no...
We provide an overview of the use of optical pulse coding to enhance the performances of long-range distributed optical fiber sensors for strain and temperature measurements. First, pulse coding techniques are introduced for distributed sensing, emphasizing in particular the advantages of advanced cyclic coding for fast distributed strain and simul...
Citations
... In the following, V9 stands for a whole cable, FIMT for a fiber in metal tube and FO for a fiber with its primary coating only. Two kinds of fiber have been used: classical bending-loss insensitive G657 single mode fibers and fluor doped fiber with a special carbon coating [23] preventing hydrogen emitted by radioactive waste or by radiolyse from entering the optical fiber and obscuring it [24]. The samples with the latter fibers are marked with an subscript "F". ...
This paper presents the measurement methodology of diameter reduction monitoring of micro-tunnel structures used for radioactive waste storage based on distributed strain measurements along fiber optic sensors installed on the circumference. The whole measurement procedure is described: the calibration of the sensors for use in harsh environment (temperature and radioactivity), the measurement analysis technique, the performance assessment of different measurement systems on a surface mock-up and the in-situ validation on an underground structure. The performances of Brillouin and Rayleigh backscattering measurements are compared, as well as different fixation technologies. Distributed measurements are compared to alternative measurements: displacement sensors, Bragg grating extensometers and MEMS accelerometers. The distributed Rayleigh backscattering measurement performed on optical cables bonded to the surface of the structure appears to be the best solution for monitoring the convergence of micro-tunnels and offers comparable performance to alternative technologies tested on the surface demonstrator.
... The opposite sequence of the exposures was not explored that extensively [29]. Also, there are not too many studies focusing on the NIR region of the spectrum (800 -1600 nm), which is commonly used for telecommunication and sensing applications [28]- [30]. ...
Optical fibers having various dopants (pure silica, fluorine, germanium and phosphorous) were consecutively exposed to ionizing radiation (gamma or beta) and hydrogen-rich environments. The attenuation spectra measured before, in-between and after the exposures displayed impacts of the radiation and hydrogen as optical loss factors. Their intermediate and ultimate losses were found to drastically depend upon the dopant type. The fibers with pure silica and fluorine-doped cores behaved as most immune to the applied conditions. The irradiated germanium-doped fibers were found to be much more sensitive to hydrogen than the as drawn fibers, which is explained by development of radiation-induced reactive sites in the fiber, that further promote interactions with hydrogen. In contrast, the irradiated phosphorous-doped fiber displayed a strong hydrogen-induced bleaching at longer wavelengths (>1000 nm), which was attributed to hydrogen reacted at P1 defect sites. A carbon coating present on one of the studied P-doped fibers was shown to prevent the bleaching.
... The opposite sequence of the exposures was not explored that extensively [29]. Also, there are not too many studies focusing on the NIR region of the spectrum (800 -1600 nm), which is commonly used for telecommunication and sensing applications [28]- [30]. ...
Optical fibers are widely used in gel-filled and Fiber-In-Metal Tube (FIMT) cables. Cable gels are believed to protect optical fibers from interactions with moisture and oxygen, while their hydrogen scavenging components reduce the hydrogen ingression in the fiber. However, if used at elevated temperatures, the gel environment may lead to the fiber coating swelling, partial dissolution, and other types of degradation. Furthermore, at high temperatures cable gels may themselves become sources of hydrogen generation. For studying potential favorable and adverse effects of cable gels, a series of optical fibers was aged in a hydrogen scavenging gel (HSG) at a pressure of 500 psi and temperatures of 50 – 300 °C. The fibers under investigation used various coatings, including dual and single acrylate, silicone/acrylate, carbon/acrylate, silsesquioxane-type hybrid, polyimide, carbon/polyimide, acrylate/PFA and polyimide/PFA. Residual coating diameter and mechanical strength of the fibers were used as an indicator of the gel influence. Effects of HSG on hydrogen ingression were evaluated from the attenuation spectra of the immersed fibers. In separate experiments, the cable gel and the fiber coatings were investigated as potential sources of hydrogen.
... Based on these previous important works on the performance of optical fiber in radiation environment, some researchers have also begun to experimentally investigate the radiation effects on the performance of different distributed fiber sensing systems, such as Optical Frequency Domain Reflectometry [9] and Raman distributed temperature fiber-based sensors [10]. However, few analyses on radiation effect on BOTDR have been reported. ...
To verify the feasibility of Brillouin optical time domain reflector (BOTDR) applied in space station, three kinds of commercial fibers, YOFC fiber (about 1 km), Corning fiber (about 1 km) and Fujikura fibers (about 1.5 km), have been radiated by Co
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in radiation experiment. Based on the Brillouin Gain Spectrum (BGS) along sensing fiber, we analyze power curve of Brillouin backscattered light, Brillouin Frequency Shift (BFS) along sensing fiber and spatial resolution carefully. The results indicate that radiation has little effect on BFS when signal-to-noise ratio (SNR) is large enough. However, since radiation will lead to radiation-induced attenuation, the amplitude of BGS will decrease accordingly. And if the SNR becomes small enough, the accurate BFS cannot be obtained. For the stressed fiber section of BOTDR, the result shows that radiation has little effect on the strain coefficient at the total radiation dose of 200 Gy, but radiation will deteriorate the spatial resolution of BOTDR with the increase of radiation dose. These results are good references for the introduction of BOTDR to space station.
... Ces deux acteurs ont mis en place l'application d'une succession de thèses, afin d'étudier les performances de ce type de capteurs à base de fibre optique. Les deux thèses précédentes avaient pour objectif l'étude des performances des capteurs (à fibre optique) en environnement sévère en utilisant aussi bien la diffusion Brillouin [10] [11] [12][13] [14] que la diffusion Raman [15] [16]. Dans le cadre de ce travail de thèse, nous attacherons une attention particulière aux effets croisés de la température et/ou de l'hydrogène en environnement radiatif que nous caractérisons en mixant les analyses et caractérisations de types : Brillouin, Rayleigh et Raman. ...
... Par conséquent, les composantes Raman Stokes et Anti-Stokes générées par le laser pompe seront affectées différemment, entraînant l'échec de l'instrument à correctement réaliser la mesure de température [14]. Pour répondre à cette problématique, plusieurs approches ont été expérimentées pour réduire l'impact de la RIA et du ΔRIA : l'utilisation de fibres résistantes aux radiations [14], la pré-irradiation de la fibre optique sous test [102], l'impact d'un pré-chargement en hydrogène [16] ...
... Dans Cigéo, les radiations seront permanentes pendant la période de surveillance et la température évoluera au sein des alvéoles. Or la plupart des travaux étudient l'influence de deux paramètres imposés l'un après l'autre et non pas simultanément : ainsi dans [14][15] [16] des fibres pré-irradiées sont placées sous température. Pour être représentatif de l'application visée et afin de poursuivre les travaux de la littérature, nous avons étudié les effets couplés de la température et de l'irradiation in-situ c'est-à-dire pendant l'irradiation de la fibre optique [121]. ...
Cette thèse a été réalisée en collaboration entre l'Andra (L’Agence Nationale pour la Gestion des Déchets Radioactifs) et le laboratoire Hubert Curien (Unité Mixte de Recherche CNRS 5516) de l’Université Jean Monnet de Saint-Étienne. Dans ce travail, j’ai évalué les performances de capteurs à fibre optique pour la surveillance du site de stockage géologique de déchets radioactifs à vie longue (projet Cigéo). Cette application demande un suivi régulier, déporté et réparti de l’évolution de différentes grandeurs d’intérêt telles que : la température, la déformation et la présence d’hydrogène (ainsi que leurs combinaisons) en environnement radiatif sévère. La solution proposée repose sur les suivis des évolutions des signatures optiques de ces guides via des études en rétrodiffusion : Brillouin, Rayleigh et Raman. Afin de répondre à cette problématique, plusieurs systèmes d’interrogations ont été testés (utilisés). Selon leurs spécificités, ils se différencient par leurs types d’analyses, leurs résolutions spatiales, leurs budget optique et portées…. La sélection des fibres optiques d’étude est un élément clés pour ce type d’applications car elles doivent résister à ces environnements extrêmes sur de longues durées. Dans ce travail, j’ai étudié les réponses de fibres optiques contenant différents dopants, en particulier Ge et F. J’ai quantifié les effets des rayonnements gamma, de la température, de la déformation et de la présence d'hydrogène sur la qualité des mesures réparties. En conclusion, mon travail a cerné le type de fibre optique à utiliser pour ces environnements sévères. Les interrogateurs conditionnent le type de fibre à utiliser ainsi que leurs longueurs et, par conséquent, permettent de bien cerner les dimensions des zones à surveiller. Les qualités des résultats de mesures sont gouvernées par les choix de plusieurs paramètres et notamment : la durée de l’impulsion, la puissance injectée dans la fibre, les pas fréquentiels, la durée de la mesure…qui se répercutent directement sur les résolutions finales (spatiales et fréquentielles) des grandeurs mesurées. Une attention particulière doit être attachée à ces critères.
... These intrinsic fibre structures have been inscribed in silica fibre for over 30 years [4] and are favoured for leveraging the intrinsic properties of the fibre in question. Bragg gratings have been implemented for applications including structural health monitoring [5,6], hydrogen detection [7] and ultrasonics [8], rendering them applicable and of interest for the domain of nuclear waste repository monitoring. ...
We present a polymer fibre Bragg grating sensor and its sensitivity to gamma radiation by observing the reflected spectral profile. The Bragg grating is femtosecond inscribed within a perfluorinated CYTOP fibre and the alteration of the Bragg wavelength corresponds to the total radiation dose received. Over a total dose of 41 k Gy, the fibre demonstrates a sensitivity of − 26.2 p m / k Gy and a resolution of 40 Gy. Under active consideration for the instrumentation of nuclear waste repositories, this study gives a better understanding of the effects of gamma radiation upon Bragg gratings in CYTOP fibres.
... Its impact is shown in Figure 20b: when the 6 MGy irradiated optical fiber is used as the sensitive element of a SE-RDTS, the ∆RIA causes a direct error on the temperature estimation, the amplitude of this error increases with the fiber distance, reaching 30°C after a short length of about 100 m. Even if this error can be reduced by an appropriate choice of the fiber [254] or by applying some correction procedure [255], standard SE-RDTS are not adapted to operate in radiation-rich environments. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t FOR REVIEW ONLY * Corresponding author: Sylvain Girard, sylvain.girard@univ-st-etienne.fr : Phone: +33 (0)477 915 812 For the sensors exploiting a DE scheme, the negative impact of the ∆RIA can be avoided at the cost of doubling the RIA impact on the sensing length [253]. ...
In this topical review, the recent progress on radiation-hardened fiber-based technologies is detailed, focusing on examples for space applications. In the first part of the review, we introduce the operational principles of the various fiber-based technologies considered for use in radiation environments: passive optical fibers for data links, diagnostics, active optical fibers for amplifiers and laser sources as well as the different classes of point and distributed fiber sensors: gyroscopes, Bragg gratings, Rayleigh, Raman or Brillouin-based distributed sensors. Second, we describe the state of the art regarding our knowledge of radiation effects on the performance of these devices, from the microscopic effects observed in the amorphous silica glass used to design fiber cores and cladding, to the macroscopic response of fiber-based devices and systems. Third, we present the recent advances regarding the hardening (improvement of the radiation tolerance) of these technologies acting on the material, device or system levels. From the review, the potential of fiber-based technologies for operation in radiation environments is demonstrated and the future challenges to be overcome in the coming years are presented.
... As detailed in [51,52], large temperature errors were observed along fibre samples exposed to hydrogen (80 °C with 202 bars of pressure for 62 h) then removed from the hydrogen tank, while the ratio between Stokes and Anti-Stokes Raman scattering (see Figure 16) was measured and interpreted in temperature following Equation (1). We also verify (Figure 16 right) that the presence of a carbon ...
... As detailed in [51,52], large temperature errors were observed along fibre samples exposed to hydrogen (80 • C with 202 bars of pressure for 62 h) then removed from the hydrogen tank, while the ratio between Stokes and Anti-Stokes Raman scattering (see Figure 16) was measured and interpreted in temperature following Equation (1). We also verify (Figure 16 right) that the presence of a carbon layer is efficient (and mandatory) to prevent hydrogen diffusion and degradation of the Raman distributed temperature sensors. ...
... Appropriate composition for the fibre (F-doped) allows reducing the amplitude of the temperature errors due to permanent effects of radiations but this is not sufficient to obtain acceptable resolution. The pre-treatments of the fiber, i.e., the ex situ pre-irradiation at 10 MGy(SiO 2 ) reduces temperature measurement error (≤2 • C) [52]. ...
This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.
... Whereas the Raman technology detects only the temperature, the Brillouin and Rayleigh scatterings are sensitive to both the applied strain and the temperature. Radiation was shown to dramatically affect the temperature sensing response based on Raman scattering in a single-ended scheme, even if radiation-hard fiber is selected [2]. For this reason, some of Andra's programs are now more focused on Brillouin and Rayleigh sensor technologies. ...
... Optical fiber sensors (OFSs) are at the cutting edge of attractive technology for integration in severe environments, especially those associated with radiation constraints. Using OFSs, it is possible to monitor a large range of environmental parameters such as temperature, strain, pressure, hydrogen presence or radiation dose [1][2][3]. These components are considered as promising candidates for monitoring in the French deep geological repository for radioactive wastes, a project called Cigéo ...
We investigated the evolution of the performances of Pulse Pre Pump-Brillouin Time Domain Analysis (PPP-BOTDA) and Tunable Wavelength Coherent Optical Time Domain Reflectometry (TW-COTDR) fiber-based temperature and strain sensors when the sensing optical fiber is exposed to two γ-ray irradiation conditions: (i) at room temperature and a dose rate of 370 Gy(SiO2)/h up to a total ionizing dose (TID) of 56 kGy; (ii) at room temperature and a dose rate of 25 kGy(SiO2)/h up to a TID of 10 MGy. Two main different classes of single-mode optical fibers have been tested in situ, radiation-tolerant ones: fluorine-doped or nitrogen-doped core fibers, as well as Telecom-grade germanosilicate ones. Brillouin and Rayleigh Sensitivities of N-Doped fibers were not reported yet, and these characterizations pave the way for a novel and alternative sensing scheme. Moreover, in these harsh conditions, our results showed that the main parameter affecting the sensor sensitivity remains the Radiation Induced Attenuation (RIA) at its operation wavelength of 1550 nm. RIA limits the maximal sensing range but does not influence the measurement uncertainty. F-doped fiber is the most tolerant against RIA with induced losses below 8 dB/km after a 56 kGy accumulated dose whereas the excess losses of other fibers exceed 22 dB/km. Both Rayleigh and Brillouin signatures that are exploited by the PPP-BOTDA and the TW-COTDR remain unchanged (within our experimental uncertainties). The strain and temperature coefficients of the various fibers under test are not modified by radiations, at these dose/dose rate levels. Consequently, this enables the design of a robust strain and temperature sensing architecture for the monitoring of radioactive waste disposals.
... As a consequence, the backscattered Stokes and anti-Stokes components generated by the same probe laser are not equally affected in the flight back to the detector, which causes the initial calibration to fail and the temperature measurement to be wrong [5]. In order to mitigate such effect several approaches were adopted: employment of radiation resistant OFs [5], applying an H 2 -loading pre-treatment to the OF sensor [6,7], using a double-ended configuration system [8,9]. Although the latter system successfully manages to retrieve correct temperature measurements, in order to maintain the performances of a single-ended system, it requires the access to both ends of the OF, a twice longer OF length and, therefore, a twice larger optical budget. ...
Raman-based Distributed Temperature Sensors (RDTS) allow performing spatially resolved (1 m) reliable temperature measurements over several km long Optical Fibers (OFs). These systems are based on the temperature dependence of the intensities of both the Stokes and anti-Stokes components of the Raman back-scattered signal. One of the specific issues associated with RDTS technology in radiation environments is the differential Radiation Induced Attenuation (RIA) between the two components that induces huge errors in the temperature evaluation. Such problem is particularly evident for commercially available single-ended DTS using one laser source. Double-ended configuration could be used to correct for the differential attenuation but are limited by RIA in terms of sensing range. In the present work, we show how a Radiation-Hardened-by-Design DTS (RHD-DTS) overcomes the observed radiation issues keeping the single-ended interrogation scheme. In the tested RHD-DTS two infrared excitation laser sources (~1550 nm and ~1650 nm) are employed: the wavelength of the Stokes component due to the first excitation source coincides with the wavelength of the second excitation; vice versa, the wavelength of the anti-Stokes component due to the second excitation source coincides with the wavelength of the first excitation. The overall result is that the two signal intensities are automatically corrected for the differential RIA all along the OF sensor length and the temperature measurements becomes robust against radiation effects. This study demonstrates the potential of such a sensor by reporting preliminary experimental results obtained with a prototype developed by Viavi Solutions exploiting radiation-sensitive or radiation-hardened optical fibers.
